1. Field of the Invention
This invention relates to pipe swivel joints, and more particularly, to pipe swivel joints having improved bearing and seal life.
2. Description of the Prior Art
The production of oil and gas from offshore wells is a common endeavor in the petroleum industry. A well or cluster of several wells is drilled in the ocean floor and fluid from these wells transported by conduit to marine tankers which transport the fluid to shore facilities. A system of pipelines convey the fluid from the wells to a platform or floating buoy to which a marine tanker may be attached. The pipeline system includes one or more pipes or conduit extending generally horizontally across the ocean floor from the wells to a point below the floating buoy and a generally vertical pipe or hose extending from the buoy to the horizontal pipe. At a plurality of locations in the pipeline system connections are needed between the various pipes. A flexible hose or an articulated loading arm secured between the buoy and a marine tanker may include one or more connections. Some of these connections are used to permit one pipe or hose to rotate relative to an adjacent pipe or hose by the use of swivel joints. Due to the action of the winds, ocean and the floating buoy these joints may experience an oscillatory motion which produces wear and failure of the joints at a rate more rapid than with a non-oscillatory motion. A fatigue failure occurs in the joints because the same area of the bearing is repetitively loaded rather than distributing the load cycle around the bearing. Elastomeric seals in the joints also tend to fail quickly in oscillatory cyclic applications when all of the oscillatory motion is applied to the seals.